Flowing wells can fail unexpectedly, the detection of which or preventative measures The Province of Alberta, Canada has over 70,000 low flow, shallow gas wells, producers annually lose 5-15% of their wintertime production due to freezing of wells and pipelines. The lost production can cost the producers in the range of $70-100 million annually. Due to the low revenue generation of individual wells, shallow gas fields and mature oil fields generally have very little instrumentation. Production measurement tends to happen at group meters and batteries, which reside throughout a field, and usually have dozens or more unmetered wells flowing into them. In the case of oil wells, the causes of failure are more numerous, including more mechanical apparatus in wells fit with pumping apparatus.
In the winter, producers watch their group meters for production drops, which typically indicate that wells upstream of the meter are frozen. Field personnel then either attempt to find the frozen wells and inject a freeze inhibitor such as methanol (methanol lowers the freezing temperature of water) in an attempt to break up the ice or simply “batch pour” methanol into wells more or less indiscriminately as a preventive measure. Methanol injection method, which has been used for decades, is often ineffective, expensive and potentially unsafe including arranging risky wintertime access to leases regardless whether wells are frozen or not.
Applicant believes, this method persists because there is currently no other solution which is not cost prohibitive. At current prices an average gas well produces $15,000-20,000 per year in revenue. Traditional instrumentation which could indicate the status of each well costs in excess of $5,000 per well. Given the large numbers of such wells, producers have not justified traditional instrumentation on most wells.
While oil wells have higher revenues, control is also more expensive, often implementing pump-off controls. It is not always economical to pump-off and related instrumentation on older lower flow oil wells.
In summer, producers note diminished flow rates from gas wells due to liquid loading in the wells and may take steps to rectify the problem by unloading the liquid from the well.